When I was thinking of switching to Taiwan Mobile (大哥大), they gave me a SIM card that was activated for 7 days so I could test out the signal at my home, work, etc. Maybe ask them if you can test it out.

I have it. The NT 388 unlimited 4G package. I’m doing what you want to do with it, not wanting to bother with a home line. It’s fine for me. The fastest speed test has been 22 mbps for me. That in reality is 2 mbps per second for downloads. Their packages are probably faster now, I got mine about 6 months ago.

Tstar won’t let foreigners sign up without a guarantor. I was just kicking the tires to see what plans they had but they immediately asked if I had a local friend who would cosign and when I said no (won’t do that out of principle) they said sorry and took the customer behind me. They will not accept deposits either.
I haven’t tried a complaint to the telecom commission but that might work however my contract with Taiwan mobile isnt up quite yet

6 years with 3 other carriers with perfect history and still get told I need a babysitter.

But now their plans aren’t really that special as the big 3 have come close with $599 unlimited 4g plans with a bigger network.